Under the Microscope

Welcome to “Under the Microscope,” Killer Nashville’s very own exclusive Forensics Corner. We will unearth, demystify, and bring you interesting, factual information about the world of forensics from experts in various fields. From dead bodies, to suspicious substances, to computers with a mind of their own, this column will explore the macabre, gory, and unexplainable with the truth in scientific terms for writers to use at their will.

This is the final installment in a three-part series by physician, author, and former Killer Nashville Guest of Honor Dr. D.P. Lyle. Through the imagined lens of a coroner, he shares critical information about the business of death and the elements of a great investigation.

The Coroner’s Most Important Determinations: Part 3

In this third and final installment in this series I will continue the discussion of “Time of Death.”

Rate of Body Decay: Putrefaction is the term used for decay or decomposition of a body. Under normal circumstances it follows a predictable pattern, which the Medical Examiner, or ME, can use in his estimation of the time of death. During the first 24 hours, the abdomen takes on a greenish discoloration, which spreads to the neck, shoulders, and head. Bloating, due to the accumulation of gas, a byproduct of the action of bacteria, within the body’s cavities and skin, soon follows. This swelling begins in the face where the features swell and the eyes and tongue protrude. The skin will then begin to marble in a greenish-black web-like pattern over the face, chest, abdomen, and extremities. This marbling occurs within the blood vessels and is due to the reaction of the blood’s hemoglobin with hydrogen sulfide. As gasses continue to accumulate, the abdomen swells and the skin begins to blister. Soon, skin and hair slippage occur and the fingernails begin to slough off. By this stage, the body has taken on a greenish-black color.

The fluids of decomposition (purge fluid) will begin to drain from nose and mouth. To the untrained eye this might look like bleeding from trauma, but is due to extensive breakdown of the body’s tissues. This process is highly dependent on temperature. In a warm garage in Texas it will occur much more rapidly than it will in a cold stream in the Rockies.

The onset and progression of decay is highly temperature dependent. A body in a Louisiana swamp might completely decay in a week or two while one in the Colorado mountains in February might not even begin its decay until the spring thaw.

Stomach Contents: After a meal, the stomach empties in approximately 2 hours and the small intestines in approximately 12 hours, depending on the type and amount of food ingested. If a victim’s stomach contains largely undigested food, then the death likely occurred within an hour or two of the meal. If the stomach is empty, the death likely occurred more than four hours after eating. If the small intestine is also empty, death probably occurred 12 hours or more after the last meal. If the ME can determine through witness statements when the last meal was consumed, he can use this to time the death.

Let’s say a man is found dead in a hotel room and the ME determines that his stomach is full of undigested food. If he had dinner with a business associate from 8 until 10 p.m., the finding of a full stomach would indicate that the death occurred shortly after he returned to his room. The ME might place the time of death between 10:00 p.m. and midnight.

The Corneas and the Vitreous of the Eyes: The clear covering over our pupils are called corneas. At death they become cloudy and opaque in a very few hours if the eyes are open at death or may take up to 24 hours if they are closed. The vitreous humor is the liquid substance that fills our eyeballs. After death the concentration of potassium within the vitreous increases at a constant rate over the first few days. Measuring the potassium level can give a general estimate of the time of death.

Insects: A dead body attracts numerous insects. These are typically flies, beetles, and other insects that feed off the corpse’s flesh. They tend to appear at predictable times and in a predictable sequence, and the ME will use this to aid in his determination of the time of death. For example, blowflies appear early, often within the first hour after death, and immediately begin to lay eggs. The eggs hatch to larvae (maggots) within hours. Over the next 10 days the larvae feed, grow, and repeatedly molt. There are tables that show the growth rate of these larvae so that the ME can compare those found at the scene with the tables of length and estimate the age of the larvae. After the larval stage the maturing flies become pupae, when their outer covering hardens. Approximately 12 days later adult flies emerge. So, this entire cycle takes from about 18 to 22 days. The mature flies will then lay eggs and the cycle repeats.

Unfortunately, these patterns vary greatly, depending upon geographic region, specific locale, time of day, weather and temperature patterns, and the season. Because of the complex nature of the bug world, the ME will often request the assistance of a forensic entomologist, a professional who studies the insects that populate a dead body. This is an extremely complex subject and can’t be adequately covered here.

Scene Markers: Scene markers are any information at the scene, or from witnesses or family and friends. Missed appointments or work, missed daily walks or visits to the coffee shop, uncollected mail or newspapers, and dated sales receipts can be useful. Even the victim’s clothing might be helpful. For example, if the victim has missed work for two days and is found near the front door of his home, dressed in work attire, and carrying his car keys, it is logical to assume that he was headed to work at the time of his death.

As you can see the determination of the time of death is complex and always a best guess. Experience and keen observation are critically important.

Along with Jan Burke, he is the co-host of Crime and Science Radio. He has worked with many novelists and with the writers of popular television shows such as Law & Order, CSI: Miami, Diagnosis Murder, Monk, Judging Amy, Peacemakers, Cold Case, House, Medium, Women’s Murder Club, 1-800-Missing, The Glades, and Pretty Little Liars.